Slashdot videos: Now with more Slashdot!

View

Discuss

Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

DeviceGuru writes "The unoccupied radio spectrum between broadcast TV channels may soon become a source of low-cost, ubiquitous broadband connectivity. Earlier this month, the U.S. Federal Communications Commission began Phase II testing of 'white space device' prototypes, to determine whether WSDs can operate without interfering with the other wireless devices commonly used in homes, offices, and public locations. A key advantage of white space wireless technology, compared to the combination of WiFI and WiMAX, is its TV-like ability to cover broad areas and penetrate walls and trees, using relatively low power levels."

With companies like Time Warner, who are both broadband providers and important content producers for broadcast TV, is there any doubt where the broadcast TV companies are going to come down on this "interference" issue?

I can hear it now:

Broadcast TV: Senator, this new scheme causes huge interference with our broadcast signalSenator: This wouldn't have anything to do with Time Warner giving you the broadcast rights to a bunch of their movies and TV shows for a song, would it?Broadcast TV: Don't be silly. We can answer any other questions you may have at the campaign fundraiser we're holding for you tonight.Senator: I think I'm beginning to appreciate your point of view.

Wow, way to RTFA. "White space" technology transmits in the gaps between broadcast TV channels. If anything, you have more potential bandwidth available than those who live in a city where many TV channels are used.

Weeeellll, no. You need transmitters to provide that whitespace in the first place, and they ain't there in the places that the OP is talking about. A place that immediately springs to mind is Pocohontas County in WV, which is a radio and TV deadzone because of the National Radio Quiet Zone. There is a single low powered AM radio station in the area and Verizon has a monopoly on cable TV, phones and broadband. It isn't going provide any advantage there.

Why would you need transmitters to provide whitespace? Whitespace is a range of frequencies where nobody transmits. Just because that whitespace is there even when there's a transmitter doesn't mean that it's provided by said transmitter! You do need a separate transmitter to provide this new service in those whitespaces, but that has nothing to do with the presence or absence of existing transmitters. Plus, at those frequencies, a transmitter could more easily provide service to rural areas, so it might in

You don't go to Pocahontas for the broadband and don't live there if you don't like roughing it at some level. Really, unless you're working at Green Bank or Snowshoe, I can't see why you would live there in the first place...

Clearly businesses want to serve the least populated areas of the country. It is in their best interests to serve the least amount of people, usually with the lowest amount of disposable income./sarcasm
If you don't like your choices of broadband and TV, then I suggest either reading more, or moving.

Could be like some of the satellite setups; use your phone for upload, TV for download. Most of the VHS/FM internet tests I've seen are really more similar to the way that sat TV works right now, they send out signals, you can choose which one you get, but there isn't really effective two-way communication.My biggest question, and one that googling doesn't want to answer, is what exactly are we talking about in bandwidth, here?TTBOMK, a HDTV VHS broadcast has about 25mbs data; thats a pretty respectable chu

This really has nothing to do with Television or TV transmitters. The idea here is that since a region does not have ALL of the TV channels (frequencies) in use, the unused frequencies could be used by other providers to deliver wireless Internet.For example: If the region has channels 2, 4, 5, 8, 11, and 13 (just VHF for this example), then the frequencies that correspond to channels 6, 7, 9, 10, and 12 could be used by wireless ISPs.

The reason this is desired is that these frequencies are much lower than

Is satellite not an option? Or is it not an option because you aren't interested in paying for it?

Anyway, I'm in what is pretty much a rural area(I'm several miles from the nearest 'city', which is really more of a town, there is a village that is closer, but it is still several miles away). I'm about 2 miles from a broadcast tower. So this solves the problem for me and my neighbors.

But is the latency slower than connecting at 26 kbps? I'll take a 500 msec latency hit if my average throughput is 200 kbps, rather than 26 kbps with 50 msec latency. Maybe I can't game, but I can get a ton more information and overall throughput.

I have satellite (Base package from WildBlue), so here are some numbers. Latency (measured by pings to google.com) measures about 1200-1600ms. Throughput (measured by downloading an Ubuntu.iso from mirrors.kernel.org) is about 60kbps. It's not bad, but it's not great either. My only other option where I live is $300/mo for a T1, which I think I'll be doing once my satellite contract runs out (and my wife lets me).

true, my parents live out in the boondocks and my dad does ALOT of stuff on ebay (grease monkey he is)and the such, and his connection runs at like 25 kbps, he has been thinking about getting the sat. internet, but that costs so much, and really is not worth the money, but he has no other options... i hope one day some broad band company will figure something out....

I have no broadband choices (I connect at 26.4kbps) but at least I get 0 over-the-air-channels. All right! Problem solved.

Just because you don't get TV channels DOES NOT mean this won't work for you. It depends on bandwidth and encoding.

For example, in amateur radio, when voice communications are insufficient, Morse code (much narrower badwidth) tends to work over great distances, and when Morse doesn't work a digital mode like PSK31 (narrower) works even better, and often at lower powers.

The formula for CW bandwidth is the bits per second (BPS) times a shape factor, K. CW speed is generally in words per minute, the word "PARIS" is the general word benchmark, 5 letters with 50 bits of information. 50/60 = 0.83 bits/second.

With a shape factor K=4, at 10 WPM (relatively slow), the signal width is about 40hz, wider than PSK31. At 25wpm (what I personally find comfortable) it's about 100hz. More experienced practitioners can speak even faster:)

I am an amateur radio operator and can attest to how easy working with VHF/UHF is on a small scale level. A 100watt VHF "repeater" on a tall hill can usually be reached 20-30 miles away with a 5 watt handheld radio and line-of-sight, and much less power for towers closer. Multipath is a problem, like anything else. Nonetheless, if the towers are properly placed so that line-of-sight is maximized (i.e. they do their homework), I have no doubt you would be able to work it with a PCMCIA laptop card and a small

Guess what? NLOS, low-power, high-bandwidth wireless technology will make it *much* more cost-effective for regional ISP's to offer service in rural areas. Right now the telco and the cableco doesnt care about rural becuase there just isnt enough density to make it profitable for them to run cable. Broadband wireless with the range of TV and without the LOS requirement will make it much easier. Plus, without the monopoly control that telco/cable has with their wires, there might actually be some competition

There are a lot of areas that have OTA TV channels without any broadband options. some people still have no options, but this does open up a lot of options for those who had none. farmers are a big one, my in-laws have this exact problem. But they can get OTA. Small townships could also benefit. heck, long-term, more competition lowers prices, and should see more expansion of DSL/Cable lines as well.

While we in rural communities who are not served by broadband, can be skipped by another technology. Yeah, TV transmitters will give internet. Too bad there's no TV transmitters around here... I have no broadband choices (I connect at 26.4kbps) but at least I get 0 over-the-air-channels. All right! Problem solved.

Well? You live in a rural area. What were you expecting? Infrastructure tends to be more effective, and therefore is more likely to be installed, where most of the people live...

The problem with this idea is that it assumes that TV broadcasting will always be done the way it is today with unused space between the channels. If "white space" equipment gets deployed it is going to create a massive problem for any attempts to change use of the existing TV spectrum. Any future users of this spectrum are going to have to work around the applications now running in what used to be the "white space".

The problem with this idea is that it assumes that TV broadcasting will always be done the way it is today with unused space between the channels. If "white space" equipment gets deployed it is going to create a massive problem for any attempts to change use of the existing TV spectrum. Any future users of this spectrum are going to have to work around the applications now running in what used to be the "white space".

If I understand correctly, part of what this device does is detect television signals and avoid spectrum that is actually being used. That is part of what is being tested. The idea is that these devices would be allowed to transmit over fairly large chunks of the spectrum, but that they would automatically detect what is actually being used for television and only transmit in the gaps between channels. That is why there's so much concern about these devices causing interference - nobody is sure how well this detection/avoidance mechanism is going to work.

If it does actually work like it is supposed to it won't matter if the white space between channels moves or vanishes - the device will stop using that chunk of spectrum and move to another. The only real problem you'd have is if you completely saturated the spectrum with television, which could happen. But in that case the devices would simply be unable to find any white space and would not be able to transmit - it wouldn't actually interfere with the television broadcast.

Between broadcast channels is a padding space meant to shield adjacent channels from sub-standard broadcasting equipment that might cause a frequency drift.This is called whitespace, unused frequencies between channels to minimize collisions. Like airplanes keeping a couple mile buffer zone between each other, to prevent a bad pilot from accidentally colliding with another plane.So even if every channel is used, there will still be some space left to squeeze a datastream into. And if this thing works as int

Between broadcast channels is a padding space meant to shield adjacent channels from sub-standard broadcasting equipment that might cause a frequency drift.

For mobile transmitters this has often been a consideration but stationary broadcast transmitters have almost always had very accurate frequency references. Before GPS timed frequency standards became available, using a local VHF TV carrier while rebroadcasting a network program as a calibration source worked even better then using WWV.

We need to subsidize fiber to every home in this country and leave the radio spectrum to mobile devices. The cost could be justified very easily by the added security and cost reductions(fire, law enforcement, and medical).

Running fibre in a subdivision where you have a house every 100 or 200 feet is one thing. Subsidizing fibre to every farmhouse, log cabin, and cottage would bankrupt the USA or Canada. Please don't compare the wide open spaces of North America with densely populated cites, or the even more densely populated cities of Europe and Asia.

This is the reason why the FCC exists and has the ability to "grant" who and what can use what spectrum. When the white space spectrum is sold, broadcasters who use it now for TV will be required by law to stop broadcasting. If Google has their way, an open standard will be developed on how to "share" this spectrum. All devices will then have to conform to this standard to use that spectrum so that they play nice with each other.Towers that currently broadcast TV will have 2 options. Either they stop se

Well, if you can find a TV that tunes to one of those frequencies rather than blanking it with a blue screen (WTF? Why do they make TVs that do that?), then you'll hear and see plenty of white noise, as you're picking up lots of background radiation.

They probably blank the screen because when I was little we used to watch scrambled spice channel (with fairly clean audio anyway). The scrambled channels now turn blue, the internet came out, and the children are safe.

I think this is a bad idea. If we start transmitting data in whitespace, words will become very difficult to distinguish from each other in any given sentence. For example "The quick red fox jumped over the brown lazy dog." by itself, is very readable. But once you transmit extra data in the whitespace it becomes: "The1quick0red1fox0jumped1over0the0brown1lazy0dog." - An invariable piece of shit. It's only a matter of time before the greedy providers decide they need more bandwidth and bleed over in to the primary data stream.

Now if we were to transmit in the margins or between the lines, that may just work!

Are they planning to have repeaters all over the place like the public wifi? If not they are going to need a lot of power. Some UHF TV stations run with a megawatt of RF. Its especially true in cities where the buildings create multipath distortion and/or block the signals entirely.

The amount of power will depend on the bandwidth and the distance to repeaters or hubs. The infrastructure would have to be similar to a cell phone network, not a single tower servicing an entire metropolitan area like the current TV broadcast system. If the power can remain low and the infrastructure designed correctly it will work, otherwise it would be a flop with consumers. No one wants to carry around a 500 watt device to communicate.

Considering the client has to respond to the incoming signal, it needs to be low power. If not, the client cannot respond with his/her 12-50mW signal. So yes, they would need repeaters, but honestly, not many (or at least a reasonable amount, considering the number of repeaters for DSL). A bigger issue would be the antenna requirements for the clients.

So with these wavelengths that can travel through walls much more easily, my internet will go down due to interference from my neighbor's automated channel search on his off-brand Korean knock-off TV?

I wonder though if this sort of technology could allow your wireless internet card to double as a wireless tv card. The same modem would take the cable data and broadcast the entire band and your computer would just sort out the data on it's end.

But it does anyway. Some methods of tuning into radio-frequency transmissions, such as superhet [wikipedia.org], create weak incidental emissions at any of several intermediate frequencies [wikipedia.org]. In countries with a TV licence [wikipedia.org], those responsible for enforcing licence compliance drive vans [bbc.co.uk] carrying equipment to detect these emissions.

I wonder though if this sort of technology could allow your wireless internet card to double as a wireless tv card. The same modem would take the cable data and broadcast the entire band and your computer would just sort out the data on it's end.

This is already true of (many) wired services. Verizon FIOS transfers both TV data and internet over the same fiber line. It's just a matter of routing different types of data and separating the different type of frames.

I would assume that the new wireless protocol will have a standard physical and MAC layer for everything that runs across it.

TV, unlike the internet, is a one-way medium. My TV may be able to pick up signals from a giant transmitter thirty miles away, and that's great. How would this work for internet connections? Something tells me that putting an antenna powerful enough to reach back to that tower inside my laptop isn't going to be too friendly with my battery life, let alone my non-shielded nuts.

It's nothing to worry about. From the FCC site: "Between January 1, 2008, and March 31, 2009, all U.S. households will be able to request up to two coupons, worth $40 each, to be used toward the future purchase of eligible testicle and ovary shields. Eligible testicle and ovary shields are for the conversion of non-shielded testicles and ovaries, and therefore are not intended for anuses connected to a paid provider such as cable or satellite TV service."

You got modded as funny but I think this is the most insightful comment on this page and I was thinking the exact same thing. That's great if we can use TV-like waves to blanket a large area with low power, reasonable bandwidth internet access. But how the hell is the upload signal going to work? My homeowner's associate even tries to prevent us from having TV antennas on our roofs (which is against the law for them to prohibit, but that's another story). But if the signal really is pretty low power, maybe a small return signal can be sent using only a modest sized/powered home antenna, who knows?

I don't think it would be that hard to transmit back. Think of your cell phone. It transmits miles away from a small, low power device. Something similar, if not identical could be used. Kind of like dish broadband, you send information by telephone line, you could send information across cellular frequencies.

Maybe like a cell phone? Last i checked, no one's got a backpack radio transmitter just to make a phone call. Cell towers pump out a good amount of juice, too, and cell phones seem to be able to talk back to them.

While I'm not an RF engineer, the equation is an unbalanced one for down- and uploads. The downlink transmitter must coverer an immense area, whereas the uplink side can be aimed. As a result you can use an extremely high gain directional antenna from your home to the main tower to achieve lower power requirements. There might even be a layered service at several different wavelengths - higher freqs for those with LOS, lower for those without.Portable devices are more troublesome, but there is the possibil

Portable devices are more troublesome, but there is the possibility of using the cell phone networks for uplink and TV for downlink. That would, of course, require interoperability and coordination between providers...which we all know would never occur.

Don't be so sure. If a progressive carrier *ahem* T-Mobile *ahem* saw limited use of their data network, I'm sure they'd partner with someone to provide the uplink if it would make them some cash.

Mobile phones manage to transmit back to their towers despite being small, low-power devices. The key: the base station's receivers are very sensitive and the coding schemes used for uplink transmission include more error detection/correction.

Granted, mobile phones don't work over the vast distances used by broadcast radio and television, but they serve as a good example of a low-power, two-way transmission system.

Seriously? Uh it's called async routing. AKA legitimate spoofing. Your outbound transmission is via land line. Satellite did this a decade ago. Your system has two IPs: in and out. Your outbound transmission essentially spoofs your inbound IP.And since we are all supposed to be good little consumers, we won't need much outbound-only bandwidth, right?

That aside there is a long list of Internetworkable features/capability that one-way transmission serves well. For example, what if they "broadcast" stock, weat

Currently, DOCSIS cable modems use a TDMA [wikipedia.org] scheme for return traffic. (Basically, divide the wavelengths up into "time slots" and each modem gets a certain time slot. The signal is generally modulated using 16-QAM. [wikipedia.org] Think of two waves offset by 90 degrees, one vertical and one horizontal. Add to that 2 levels of amplitude for each wave. So, you can have 16 combinations. Or 4 bits for each wavelength of signal. You can increase the numbers of levels of different amplitude to increase your possible bit combinat

Why do these companies get to use this spectrum for free, when the telcos, cable operators, Paul Allen, etc. are currently bidding billions for similar frequencies? That last sentence should read:

A key advantage of white space wireless technology, compared to the combination of WiFI and WiMAX, is its TV-like ability to cover broad areas and penetrate walls and trees, using relatively low power levels for free."

Isn't there just as much bandwidth between 3Ghz and 4Ghz as there is between 0Ghz and 1Ghz? Why do we carve out larger chunks at higher frequencies? It seems to me that the real answer is finer-grained transmitters and receivers.

There is actually more bandwidth between 3GHz and 4Ghz than 0Ghz and 1Ghz. Say you were to pick 100mhz wide channel right in between those ranges. 3.5ghz has 7 times the amount of cycles/sec than 500mhz. So assuming PCM and no losses, that's 7 times the bandwidth.

There is actually more bandwidth between 3GHz and 4Ghz than 0Ghz and 1Ghz. Say you were to pick 100mhz wide channel right in between those ranges. 3.5ghz has 7 times the amount of cycles/sec than 500mhz. So assuming PCM and no losses, that's 7 times the bandwidth.

When you want to send a signal on a 100 mHz wide channel, you would first construct a signal that uses frequencies between 0 and 100 mhz. Then you can shift it up by 450 mHz and get a 100mHz channel centered at 500 mHz, or shift it up by 100 gHz to each frequency and get a 100 mhz channel centered at 100.05 gigahertz. But it's still the same bandwidth and capacity.

The truth is that there is no effective limit to the bandwidth available other than the limits we arbitrarily decide. There are an infinite number of frequencies between 1 Khz and 2 Khz. On a given frequency, the amount of information that can be transferred increases with the frequency, so while there's an infinite number of frequencies between any point and any other, the amount of data that can be transferred on a given frequency rises as the frequency increases.So, assuming that all the bandwidth betwee

Hi. I thought that too and was providing a simple example. However, everyone else here on Slashdot is trying to tell me that the amount of information that can be transferred stays the same regardless of frequency.

No, information carrying capcity, (also referred to as "bandwidth" confusingly), is proportional to the analog frequency range, (which was the original "bandwidth" concept). Check the wikipedia article. There are physics-related reasons for this, but I'm not that much of a physicist:
http://en.wikipedia.org/wiki/Bandwidth [wikipedia.org]

That is usually not a limitation because it's based on the carrier frequency the data is being placed on along with the modulation techniques in use. Using some cool modulation schemes I can put 2Gbps of data onto a 1 GHz carrier and the cycle rate is not a factor. Remember there is a difference between the data rate and the symbol rate (actually changes to the sine wave). A 2 Gbps digital signal can equate to a much smaller symbol rate based on the modulation in use. Many cable modems use either a 16 QA

The key is that each of those cycles is *not* a potential bit. Radio communication is inherently different from RS232 or other simple wired standards (the newer ones are more complicated and borrow quite a bit from techniques developed for radio).

The primary difference is that bandwidth is limited. This means that you can't use every cycle. In the simplest case (ASK) you take the signal you want to transmit (which would be similar to your 800baud RS232 signal), and then remove the high frequency componen

Higher frequencies get attenuated by walls, rain, trees, etc... more easily than the lower ones. Yes the higher frequencies have more available bandwidth but there are disadvantages. TFA mentions the pros of using the UHF and VHF spectrum.

3GHz is a fairly high frequency in the microwave region. It won't penetrate walls or the weather very well compared to frequencies 1GHz. This is why your cell phone operates closer to 1GHz.C-band downlinks, for example, operate between about 3.7 and 4.2 GHz. This is why you can get a satellite dish and point it around at different 'birds' to get different sets of channels. They're very directional. Higher frequencies don't really help you if you're trying to cover a wide area. There's plenty of spectrum "av

Uhh... I was under the impression that finer grained transmitters were exactly what all this whitespace hubbub was about. Because FM is FM, a given carrier frequency uses the adjacent frequencies. To allow stuff to actually work, there is some amount of a required gap between these carrier frequencies. The mandated gap is actually greater than necessary, and this is the white space.Finer grained transmitters is exactly what TFA is talking about, and it is a fairly real answerer. That, or I'm talking ou

Your right, but different frequency ranges have different properties. The 700Mhz range tends to go through walls and such while the 2.4Ghz range (near our friendly microwave frequency) doesn't pass through solid objects as well.

Think of sound. A base speaker goes through walls etc. while a high frequency sound can be blocked by your hand being put right in front of the speaker.

At high frequencies radio waves take on the properties of light waves. They just bounce off of stuff rather than go through it. 3 and 4 GHz needs line-of-sight to really work well. The lower frequencies, such as VHF television, propagate much better through materials and depend a little less on line-of-sight. It would work better over longer distances.

This is basically the same argument as "why have cell phone service? Let's just have TCP/IP data and let people run VoIP over it!", except you'd substitute VoIP for "multicast video streaming". I think, eventually, we'll get there, but one thing at a time.

We have come full circle.I remember, back when I was a youth, and TV was just over the air, the Sunday afternoon ritual of standing outside with my father during football season, making adjustments to an ever complicated contraption of antenna.

All manners of materials and shapes were experimented on, and my mother would yell, "better", "worse", or, "oh my god", depending on just how our adjustments altered the picture.

Now, my son and I will be standing outside, in the not too distant future, adjusting the a

Broadcasters are avoiding channels 2 through 6 when given a choice which channels to select after the digital switchover. There will be almost no TV stations in that band in the USA after Feb 17, 2009 (and in Canada after Aug 31, 2011). That's 30 mhz of usuable frequency space (not counting the 4-mhz gap between channels 4 and 5).

While these frequencies may not be so great for a 6mhz wide TV channel, they're perfectly usable for digital internet. And you're guaranteed no interference with TV, because there won't be any TV stations in that spectrum.

You asked your grandparents why there isn't a channel 1... your grandchildren will be asking you why there aren't any channels 1-through-6.

My big concern is that some of the TV space is used for wireless microphones and monitors in theater, live sound and conferences. There's a huge amount of that hardware deployed already, much of it unable to change frequency past a relatively narrow band. Since it's low-power one can conceive the signal not always being detected by other white space hardware. With the signal being analog instead of digital, interference can really matter.